Will Power led a Penske one-two-three as practice officially began for the 2014 Indianapolis 500.
The Australian topped the charts with a tow-assisted best average lap speed of 223.057mph, edging out team-mates Juan Pablo Montoya (222.502mph) and Helio Castroneves (222.373mph).
"It's great to be at the top of the speed charts, but the car felt really good too, and we got to do quite a few laps," Power said.
"We were just anticipating that it might be wet the next couple of days. It's only practice, first day, [but it's] always handy to be at the top."
On an afternoon when many cars only opted for brief shakedown runs and 10 of the 33 entries did not run at all, the Penske Dallara-Chevrolets were among the few cars to complete a solid day's worth of running, with the three cars covering a combined 197 laps.
JR Hildebrand was fourth-fastest in his first run out in the second Ed Carpenter car, with Ryan Hunter-Reay ending the day in fifth for Andretti.
NASCAR star Kurt Busch's official preparations began with the Andretti driver going 12th fastest at 220.352mph and embracing the opportunity to understand how the car works in dirty air.
"Our car definitely changed," he said. "The attitude and dirty air... it's exciting because every corner is different. And you have to remember where each of those moments [were] from the lap before; and then continue to gain more information and digest what just happened in the next lap.
"And things are moving quickly at 220, and that was with just a few cars [on the track]. So I know there's going to be more dirty air and there's going to be tougher conditions."
Last year's winner Tony Kanaan competed a dozen laps to finish up 10th-fastest, while Brickyard returnee Jacques Villeneuve ticked off 70 laps on his way to 14th.
Prior to the track being opened for official practice, Sage Karam completed the final phase of his rookie orientation, clearing the way for the Ganassi rookie's participation in the 500.
Pos Driver Team/Engine Speed Time Gap Laps 1. Will Power Penske/Chevy 223.057 40.3485s 82 2. Juan Pablo Montoya Penske/Chevy 222.502 40.4490s +0.1005s 32 3. Helio Castroneves Penske/Chevy 222.373 40.4726s +0.1241s 83 4. JR Hildebrand Carpenter/Chevy 222.200 40.5040s +0.1555s 24 5. Ryan Hunter-Reay Andretti/Honda 222.134 40.5160s +0.1675s 47 6. EJ Viso Andretti/Honda 222.105 40.5214s +0.1729s 28 7. Charlie Kimball Ganassi/Chevy 221.845 40.5689s +0.2204s 12 8. Ed Carpenter Carpenter/Chevy 221.772 40.5822s +0.2337s 47 9. Townsend Bell KV/Chevy 220.840 40.7534s +0.4049s 19 10. Tony Kanaan Ganassi/Chevy 220.755 40.7691s +0.4206s 12 11. Carlos Munoz Andretti/Honda 220.581 40.8013s +0.4528s 36 12. Kurt Busch Andretti/Honda 220.352 40.8437s +0.4952s 31 13. Scott Dixon Ganassi/Chevy 220.226 40.8671s +0.5186s 11 14. Jacques Villeneuve Schmidt/Honda 220.070 40.8960s +0.5475s 70 15. Ryan Briscoe Ganassi/Chevy 219.745 40.9566s +0.6081s 15 16. Alex Tagliani Fisher/Honda 219.557 40.9917s +0.6432s 25 17. Oriol Servia Rahal/Honda 219.150 41.0678s +0.7193s 5 18. Marco Andretti Andretti/Honda 218.447 41.2000s +0.8515s 6 19. Takuma Sato Foyt/Honda 217.840 41.3147s +0.9662s 13 20. Graham Rahal Rahal/Honda 217.454 41.3881s +1.0396s 16 21. Sage Karam Ganassi/Chevy 217.310 41.4154s +1.0669s 77 22. Josef Newgarden Fisher/Honda 216.257 41.6172s +1.2687s 5 23. Martin Plowman Foyt/Honda 216.165 41.6348s +1.2863s 30 All drivers use Dallara chassis